A. Field of the Invention
This invention relates to mesoporous aluminophosphate materials that are modified with at least one element selected from zirconium, cerium, lanthanum, manganese, cobalt, zinc, and vanadium. The materials have high surface area and excellent thermal and hydrothermal stability, with a relatively narrow pore size distribution in the mesoporous range.
Methods for producing the modified aluminophosphate materials also are disclosed. Advantageously, this material can be used as a support for a cracking catalyst, for example, in a fluid catalytic cracking process.
B. Description of the Prior Art
Amorphous metallophosphates are known and have been prepared by various techniques. One such material is described in U.S. Pat. No. 4,767,733. This patent describes rare earth aluminum phosphate materials, which, after calcination, have a relatively broad pore size distribution with a large percentage of pores greater than 150 xc3x85. The typical pore size distribution is as follows:
U.S. Pat. Nos. 4,743,572 and 4,834,869 describe magnesia-alumina-aluminum phosphate support materials prepared using organic cations (e.g., tertiary or tetraalkylammonium or phosphonium cations) to control the pore size distribution. When organic cations are used in the synthesis, the resulting materials have a narrow pore size distribution in the range from 30 to 100 xc3x85. When they are not used, the pore size is predominantly greater than 200 xc3x85. U.S. Pat. No. 4,179,358 also describes magnesium-alumina-aluminum phosphate materials, materials described as having excellent thermal stability.
The use of aluminophosphates in cracking catalysts is known. For example, U.S. Pat. No. 4,919,787 describes the use of porous, rare earth oxide, alumina, and aluminum phosphate precipitates for catalytic cracking. This material was used as part of a cracking catalyst, where it acted as a metal passivating agent. The use of a magnesia-alumina-aluminum phosphate supported catalyst for cracking gasoline feedstock is described in U.S. Pat. No.4,179,358. Additionally, a process for catalytic cracking high-metals-content-charge stocks using an alumina-aluminum phosphate-silica-zeolite catalyst is described in U.S. Pat. No. 4,158,621.
There remains a need in the art for highly stable aluminophosphate materials for use in catalytic cracking processes, as well as for simple, safe processes for producing these materials. The aluminophosphate materials preferably possess excellent hydrothermal and acid stability with uniform pore sizes in the mesoporous range, and provide increased gasoline yields with increased butylene selectivity in C4xe2x88x92 gas.
This invention relates, in a first aspect, to a mesoporous aluminophosphate material comprising a solid aluminophosphate composition modified with at least one element selected from zirconium, cerium, lanthanum, manganese, cobalt, zinc, and vanadium, wherein the mesoporous aluminophosphate material has a specific surface of at least 100 m2/g, an average pore diameter less than or equal to 100 xc3x85, and a pore size distribution such that at least 50% of the pores have a pore diameter less than 100 xc3x85.
Preferably, the mesoporous aluminophosphate material has an average pore diameter of 30 to 100 xc3x85.
The invention also relates to a method of making the mesoporous aluminophosphate material described above, the method comprising the steps of:
(a) providing an aqueous solution containing a phosphorus component; an inorganic aluminum containing component; and an inorganic modifying component containing at least one element selected from zirconium, cerium, lanthanum, manganese, cobalt, zinc, and vanadium;
(b) adjusting the pH of said aqueous solution into the range of about 7 to about 12 so that a solid material is precipitated from said solution; and then
(c) recovering the solid material from said solution, wherein the solid material includes the mesoporous aluminophosphate material.
Preferably, the inorganic aluminum containing component includes sodium aluminate and the method includes the further step of lowering the sodium level of the solid material recovered in step (c). This may be achieved by ion exchange with an ammonium salt or an acid. Typically, the sodium level of the final aluminophospate material is less than 1.0 wt % Na.
Preferably, the method includes the further step of exposing the aqueous solution, after step (b) but before step (c), to hydrothermal or thermal treatment at about 100xc2x0 C. to about 200xc2x0 C. to facilitate uniform pore formation.
Advantageously, the solid materials according to the invention can be used as solid support materials for fluid catalytic cracking (xe2x80x9cFCCxe2x80x9d) catalysts.